Soviet-Controlled Fusion

The most exciting current subject in applied physics is "controlled fusion," i.e., getting usable energy out of the nuclear reactions that make H-bombs explode. Industrialists looking forward to atomic power are just as interested in fusion as physicists are. If controlled power can be extracted from hydrogen or other light elements, it may prove much cheaper than power from uranium.

Neither physicists nor industrialists have been learning much about fusion. The U.S. Atomic Energy Commission keeps the whole subject rigidly secret. The British fusion program has been kept secret too.

Last week Russian Physicist Igor V. Kurchatov, speaking at Britain's Harwell Atomic Energy Research Establishment, brought the subject of controlled fusion into the open. As early as 1950, said Kurchatov, Soviet scientists made theoretical studies about it. They started actual laboratory work in 1952, the year the U.S. achieved its first full-scale thermonuclear explosion.

In his speech Kurchatov obviously did not tell all he knows, but he did make a closer public approach to one aspect of controlled fusion than anyone has made before. Far from sticking to generalities, he went into technical detail--with photographs, curves and figures.

Pinch Effect. The big problem in controlled fusion is to reach the necessary high temperature (millions of degrees) without melting or vaporizing the walls of the container. Kurchatov told how Russian scientists experimented elaborately with one of the most promising methods, the "pinch effect." When a powerful electric current is sent through an ionized gas in a tube, it creates a magnetic field that compresses the gas into the tube's center, keeping it away from the walls.

Scientists of all countries know about the pinch effect, but their work with it has been minor, or is still secret. According to Kurchatov, the Russians made a big effort and got some remarkable results. By sending very heavy currents in short pulses through tubes containing such gases as deuterium (heavy hydrogen), they concentrated the gas in the center of the tube and held it there for an appreciable instant, while its temperature rose toward 1,000,000DEG C.

At this temperature, deuterium nuclei can react with one another at a rather slow rate. So when the Soviet scientists detected both free neutrons and high-energy X rays coming from the tube, they thought at first that they had started a true thermonuclear reaction. More careful investigation proved that this could not be the case, but free neutrons are the "fire" that cause most nuclear transformations, and any new process that frees them is apt to prove important.

"Other Possibilities." Kurchatov did not claim that the Russians have accomplished much with their pinch-effect experiments. He pointed out that it had not yet proved possible to keep the hot gas out of contact with the walls of the tube for more than a fraction of a second. "The success of further work in this direction," he said, "will greatly depend on the possibility of creating conditions under which the plasma [ionized gas] column will experience multiple oscillations during the buildup of the current without coming in contact with the walls. However, there are serious reasons to believe that this cannot be achieved."

Kurchatov's last paragraph must have tantalized his Harwell listeners: "On appraising the various approaches to the problem of obtaining intense thermonuclear reactions, we do not deem it possible to completely exclude further attempts to attain this goal by using pulsed discharges. However, other possibilities must also be carefully considered. Especially interesting are those in which the idea of stationary processes may be used."

When Kurchatov finished, the Harwell researchers gave him an ovation. British newspapers proclaimed that the Russians are close to success in harnessing fusion power, and are far ahead of the U.S. and Britain. Kurchatov's speech did not justify any such conclusion. What it did prove is that Soviet scientists 1) have been doing ambitious and interesting work on controlled fusion, and 2) they are not compelled to keep all their results secret.

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